Motion Reference Unit and Inertial Navigation Systems

This is a typical configuration, with the inertial sensors mounted close to the sonar head.

The inertial sensor is connected to the Navsight GNSS which integrates a survey grade dual antenna GPS/GNSS receiver.
Navsight GNSS fuses real time inertial data with GNSS information and transmits this data to a computer and sonar.

The Motion Reference Unit (MRU) provides roll, pitch, and heave. Heading and position are provided by the GNSS receiver. Data are provided to the Echosounder.
The Inertial Navigation System (INS) fuses all inertial data with GNSS information in real-time to provide the echo-sounder with more robust data. Indeed, if there is a communication cut, or a GNSS outage, due to a bridge crossing for instance, the Inertial Navigation System will maintain the position information until a new fix is acquired.

If you mount the inertial sensor in the cabin, you can choose the surface models (A, E, N, or D). If you prefer installing the inertial sensor close to the echo-sounder head, then a titanium enclosure is required (Navsight subsea models). If you install the sensor on board, then a subsea enclosure will be preferred as well. Even though the surface enclosure is IP68, salt water can damage it if long exposure, or not cleaned.

When wave frequency is erratic or in case of long period swell, the delayed heave feature can save the day by allowing survey in rough conditions. This algorithm allows a more extensive calculation, resulting in a heave accurate to 2.5 cm for Ekinox sensors, and 2 cm for Apogee. Delayed heave data are displayed in real-time with a little delay.

Apogee-D integrates a tri-frequency receiver compatible with TerraStar and Veripos. In addition to these positioning services, MarineStar and OmniStar are also available when buying the Navsight Solution. Specify to the SBG rep which positioning service is desired for your operation.